Thermodynamic: Conservation of Energy Question

[halide]

Homework Statement

The mixing tank shown here initially contains 50 kg of water at 25°C. Suddenly the two valves and the single outlet valve are opened so that two water streams, each with a flow rate of 5 kg/min, flow into the tank, and a single exit stream with a flow rate of 10 kg/min leaves the tank. The temperature of one inlet stream is 80°C, and that of the other is 50°C. the tank is well mixed, so that the temperature of the outlet stream is always the same as the temperature of the water in the tank.

My (wrong) approach

I let the final temperature be T, and tried to find the equilibrium temperature using heat capacity. However, I am unable to get the correct answer.

 

[rude man]

What answer did you get? Show your work.